MicroRNA-31-5p Attenuates Doxorubicin-Induced Cardiotoxicity Via Quaking And Circular RNA Pan3

Objective Doxorubicin(DOX)is a broad-spectrum anticancer chemotherapeutic drug.However,its cumulative dose of cardiotoxicity has greatly limited the clinical application of DOX.Although studies have shown that multiple signalling pathways are involved in DOX-induced cardiac injury,the exact mechanism of DOX-induced cardiotoxicity remains unclear.Understanding more about the underlying mechanisms of DOX cardiotoxicity will help improve its clinical application.MicroRNA(miRNA)can negatively regulate target genes at the post-transcriptional level by inhibiting mRNA translation or promoting mRNA degradation,and miRNA is involved in the occurrence and development of various diseases.Increasing evidence suggests that mi RNAs have important roles in heart development,ventricular hypertrophy,arrhythmia after heart attack,and heart failure.In addition,miRNAs are closely related to DOX-induced cardiotoxicity.However,the role of miR-31-5p in DOX-induced cardiotoxicity is unclear.Circular RNA(circRNA),which is characterized by a covalently closed circular structure,is essential in various biological processes.CircRNA can recruit other RNAs and,by binding to them,affect the transcription,translation,and / or degradation of specific mRNAs.However,how circRNA is involved in cardiotoxicity needs further study.Quaking(QKI)is an RNA-binding protein(RBP)that regulates a variety of RNA processes,such as pre-mRNA splicing,miRNA expression and circRNA formation.Although QKI may play a protective role in DOX-induced cardiotoxicity,the upstream regulatory mechanism of QKI is still unclear and needs further research.Therefore,study about QKI upstream may provide new treatment strategies for patients with DOX-induced cardiotoxicity.Method and results Models of DOX cardiotoxicity in cultured cardiomyocytes and mice were used.MicroRNA-31-5p and circular RNA(circRNA)levels were determined by Quantitative Real-time PCR(qRT-PCR),and we found that DOX treatment up-regulated miR-31-5p expression and significantly reduced circPan3 expression both in H9c2 cells and mice heart.The expression of QKI was detected by immunoblot in cultured cardiomyocytes and mice heart tissues.Combined with database as TargetScan,a double luciferase reporter gene analysis was performed to verify that miR-31-5p can directly target and regulate the expression level of QKI.And the down regulated expression of circPan3 is due to the silence of miR-31-5p on QKI.Through TUNEL(TdT mediated dUTP Nick End Labeling)staining and caspase 3/7 activity detection,we found that silencing of miR-31-5p significantly reduced myocardial cell apoptosis induced by DOX.As miRNAs and circRNAs could be serum diagnostic markers we further detected the serum levels of mi R-31-5p and circPan3.We found that DOX treatment increased miR-31-5p expression levels and decreased circPan3 expression levels in mice serum.Considering that DOX not only lead to cell death by apoptosis but also necrosis,by detecting the High mobility group box 1(HMGB1)protein,we found that miR-31-5p,QKI,and circPan3 are also involved in DOX-induced necrosis.After ADV2 miR-31-5p antagomir injection,DOX induced miR-31-5p expression levels significantly decreased,however,QKI and circPan3 expression levels significantly increased.Cardiac apoptosis as well as cardiac function and myocardial fibrosis of mice were significantly alleviated after miR-31-5p was silenced.Conclusion In summary,our data suggest that miR-31-5p,QKI,and circPan3 are associated with DOX-induced cardiotoxicity.MiR-31-5p negatively regulates the expression of circPan3 by directly inhibiting QKI expression in DOX-induced cardiotoxicity.